How can I run an XPath on a very large file?

[JerryShea]

My program runs out of memory when I do this:

string filename = @"large.xml";
XPathDocument doc = new XPathDocument(filename);
XPathNavigator nav = doc.CreateNavigator();
XPathNodeIterator iterator = nav.Select("//items/item");
while (iterator.MoveNext()) {
....
}

I get the same behaviour with other XPathDocument constructors too.

Can anyone advise how to do an XPath on an XML stream rather than a document?

[Oleg Tkachenko [MVP]]

JerryShea wrote:

My program runs out of memory when I do this:

string filename = @"large.xml";
XPathDocument doc = new XPathDocument(filename);
XPathNavigator nav = doc.CreateNavigator();
XPathNodeIterator iterator = nav.Select("//items/item");
//items/item is one of the worst XPath expressions. Always avoid using
// if you care about perf.
I get the same behaviour with other XPathDocument constructors too.

Can anyone advise how to do an XPath on an XML stream rather than a document?

To select item elements children of items element you don't need
XPathDocument, it can be easily implemented with XmlTextReader.
If you do need XPath, take a look at XPathReader.
--
Oleg Tkachenko [XML MVP]
http://blog.tkachenko.com

[JerryShea]

thanks a lot Oleg. The XPathReader is just the ticket

"Oleg Tkachenko [MVP]" wrote:

JerryShea wrote:

My program runs out of memory when I do this:

string filename = @"large.xml";
XPathDocument doc = new XPathDocument(filename);
XPathNavigator nav = doc.CreateNavigator();
XPathNodeIterator iterator = nav.Select("//items/item");

//items/item is one of the worst XPath expressions. Always avoid using
// if you care about perf.

I get the same behaviour with other XPathDocument constructors too.

Can anyone advise how to do an XPath on an XML stream rather than a document?

To select item elements children of items element you don't need
XPathDocument, it can be easily implemented with XmlTextReader.
If you do need XPath, take a look at XPathReader.
--
Oleg Tkachenko [XML MVP]
http://blog.tkachenko.com